The United States believes Israel has conducted an airstrike into Syria, two U.S. officials tell CNN.

And:

The Israelis have long said they would strike at any targets that prove
to be the transfer of any kinds of weapons to Hezbollah or other
terrorist groups, as well as at any effort to smuggle Syrian weapons
into Lebanon that could threaten Israel.

In reality, the "other terrorists groups" Israel claims to worry about, are indeed funded and directed by the US, Israel, and Saudi Arabia as part of a long-standing, documented conspiracy to overthrow the nations of Iran and Syria.
Reported by Pulitzer Prize-winning journalist Seymour Hersh in his 2007 New Yorker article, "The Redirection," it was stated (emphasis added):

"To undermine Iran, which is predominantly Shiite, the Bush
Administration has decided, in effect, to reconfigure its priorities in
the Middle East. In Lebanon, the Administration has coöperated with
Saudi Arabia’s government, which is Sunni, in clandestine operations
that are intended to weaken Hezbollah, the Shiite organization that is
backed by Iran. The U.S. has also taken part in clandestine operations
aimed at Iran and its ally Syria. A by-product of these activities has
been the bolstering of Sunni extremist groups that espouse a militant
vision of Islam and are hostile to America and sympathetic to Al Qaeda."

Of Israel it specifically stated:

"The policy shift has brought Saudi Arabia and Israel into a new
strategic embrace, largely because both countries see Iran as an
existential threat. They have been involved in direct talks, and the
Saudis, who believe that greater stability in Israel and Palestine will
give Iran less leverage in the region, have become more involved in
Arab-Israeli negotiations."

Additionally, Saudi Arabian officials mentioned the careful balancing
act their nation must play in order to conceal its role in supporting
US-Israeli ambitions across the region:

"The Saudi said that, in his country’s view, it was taking a political
risk by joining the U.S. in challenging Iran: Bandar is already seen in
the Arab world as being too close to the Bush Administration. “We have
two nightmares,” the former diplomat told me. “For Iran to acquire the
bomb and for the United States to attack Iran. I’d rather the Israelis
bomb the Iranians, so we can blame them. If America does it, we will be
blamed.”"

This, in fact, reveals the true nature of the attacks, a result of US, Saudi, and Israeli proxies failing inside of Syria and the desperate need to carryout military intervention to save them, while leaving intact whatever remaining legitimacy and plausible deniability the US holds globally, and Saudi Arabia holds across the Muslim World.

What Israel's Strike May Really Mean

Indeed, Israel's explanation as to why it struck neighboring Syria is
tenuous at best considering its long, documented relationship with
actually funding and arming the very "terrorist groups" it fears
weapons may fall into the hands of.

In reality, the pressure placed on Syria's borders by both Israel and
its partner, Prime Minister Recep Tayyip Erdoğan's Turkey in the north,
is part of a documented plan to relieve pressure on the Western,
Israeli, Saudi-Qatari armed and funded terrorists currently collapsing inside Syria.

Image: The Brookings Institution, Middle East Memo #21 "Assessing Options for Regime Change (.pdf)," makes no secret that the humanitarian "responsibility to protect" is but a pretext for long-planned regime change.

....

Brookings describes how Israeli
efforts in the south of Syria, combined with Turkey's aligning of vast amounts
of weapons and troops along its border to the north, could help effect violent regime change
in Syria:

"In addition, Israel’s intelligence services have a strong knowledge of
Syria, as well as assets within the Syrian regime that could be used to
subvert the regime’s power base and press for Asad’s removal. Israel
could posture forces on or near the Golan Heights and, in so doing,
might divert regime forces from suppressing the opposition. This posture
may conjure fears in the Asad regime of a multi-front war, particularly
if Turkey is willing to do the same on its border and if the Syrian
opposition is being fed a steady diet of arms and training. Such a
mobilization could perhaps persuade Syria’s military leadership to oust
Asad in order to preserve itself. Advocates argue this additional
pressure could tip the balance against Asad inside Syria, if other
forces were aligned properly." -page 6, Assessing Options for Regime Change, Brookings Institution.

In regards to Iran, in Brookings' "Which Path to Persia?" report, it states specifically (emphasis added):

"Israel appears to have done extensive planning and practice for such a
strike already, and its aircraft are probably already based as close to
Iran as possible. as such, Israel might be able to launch the strike in a
matter of weeks or even days, depending on what weather and
intelligence conditions it felt it needed. Moreover, since Israel would
have much less of a need (or even interest) in securing regional
support for the operation, Jerusalem probably would feel less motivated
to wait for an Iranian provocation before attacking. In short, Israel
could move very fast to implement this option if both Israeli and
American leaders wanted it to happen.

However, as noted in the previous chapter, the airstrikes themselves are really just the start of this policy. Again, the Iranians would doubtless rebuild their nuclear sites. They would probably retaliate against Israel, and
they might retaliate against the United States, too (which might create
a pretext for American airstrikes or even an invasion)." -page 91, Which Path to Perisa?, Brookings Institution.

And in this statement we can gather insight behind both Israel's otherwise irrational belligerent posture
throughout its brief history, as well as its more recent acts of
unprovoked aggression against Syria. Israel's role is to play the "bad
guy." As a regional beachhead for Western corporate-financier interests,
it provides a "foot in the door" to any of the West's many desired
conflicts. By bombing Syria, it hopes to provoke a wider conflict - an
intervention the West has desired and planned for since it tipped off
Syria's violent conflict in 2011.

For Syria and its allies - the goal now must be to deter further Israeli
aggression and avoid wider conflict at all costs. If NATO's proxy
terrorist forces are as weak as they appear - incapable of tactical or
strategic gains, and tapering off into desperate terrorist attacks, it
is only a matter of time before NATO's campaign grinds to a halt. As mentioned before,
such a failure on NATO's part will be the beginning of the end for it,
and the Western interests that have been using it as a tool to achieve
geopolitical hegemony.

Israel should be expected to commit to increasingly desperate acts to
provoke Syria and Iran - as its leadership represent directly
corporate-financier interests abroad, not the Israeli people, or their
best interests (including peace and even survival). For the people of
Israel, they must realize that their leadership indeed does not
represent them or their best interests and is able, willing, and even
eager to spend their lives and fortunes in the service of foreign, corporate-financier interests and global hegemony.